Beam steering devices

ABSTRACT

A beam steering device includes a substrate with a first refractive index that defines a cavity, an electroactive material in the cavity that has a variable refractive index, and two sets of opposing overlays. The overlays in one set of opposing overlays are parallel to each other, while the overlays in the other set are tilted with respect to each other. This allows one or more electric fields between the overlays to be used to align the electroactive material in two different directions to change its refractive index, allowing for a faster speed of beam steering through refraction than conventional approaches.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a bypass continuation of PCT Application No.PCT/US2019/062110 filed Nov. 19, 2019, titled “BEAM STEERING DEVICES,”which claims priority to U.S. Provisional Application No. 62/769,052filed Nov. 19, 2018, titled “FAST BEAM STEERING DEVICE USINGMULTI-DIMENSIONAL ELECTRIC FIELDS AND OVER-DRIVING,” the entiredisclosures of which are incorporated herein by reference.

BACKGROUND

Current liquid crystal-based beam steering devices use an electric fieldto alter the orientation of the liquid crystal molecules. The liquidcrystal molecules align with the direction of the electric field.Anchoring forces created by an alignment layer return the liquid crystalmolecules to their original orientation when the electric field isremoved. Increasing the amplitude of the electric fields increases thespeed of rotation of the liquid crystal molecules, but the alignmentlayer forces are fixed, so the change in orientation when the electricfield is removed occurs relatively slowly, regardless of the fieldamplitude. This causes a conventional liquid-crystal beam steeringdevice to switch slowly from an “ON” state to an “OFF” state, regardlessof how quickly the device switches from “OFF” to “ON.”

SUMMARY

A beam steering device includes a substrate defining a cavity and havinga first refractive index, and an electroactive material, disposed withinthe cavity and having a variable refractive index. The beam steeringdevice also includes a first overlay, coupled to the substrate, toreceive an incident light beam orthogonal to a first plane of the firstoverlay and to couple the incident light beam into the electroactivematerial. The beam steering device also includes a second overlaycoupled to the substrate and defining a second plane tilted with respectto the first plane to define a tilt angle between the first plane andthe second plane. The second overlay receives the incident light beamfrom the electroactive material and outputs, after refraction, theincident light beam as an output light beam.

A method for projecting a light beam on a retina of a user via eyewearworn by the user includes receiving, via a network overlay of theeyewear, image data and/or video data from a remote device. The methodfurther includes converting, via a source of the eyewear, the image dataand/or video data into a light beam. The method further includescoupling, into a beam steering device of the eyewear, the light beam asan incident light beam orthogonal to a first plane of a first overlay ofthe beam steering device. The first overlay is coupled to a substrate ofthe beam steering device. The substrate has a first refractive index anddefines a cavity having an electroactive material disposed therein, theelectroactive material exhibiting a variable refractive index. Themethod also includes receiving, at a second overlay of the beam steeringdevice, the incident light beam from the electroactive material, thesecond overlay defining a second plane titled with respect to the firstplane to define a tilt angle. The method further includes applying afirst electric field to the electroactive material between the firstoverlay and the second overlay, and a second electric field to theelectroactive material between a third overlay and a fourth overlay ofthe beam steering device. The third overlay and the fourth overlay eachdefine a plane orthogonal with respect to the first plane, such that theelectroactive material attains a second refractive index based on astrength of the first electric field and the second electric field. Themethod also includes outputting, after refraction by the second overlay,the incident light beam as an output light beam onto the retina of theuser.

A scanning system includes a set of beam steering devices in cascade.Each beam steering device includes a substrate defining a cavity andhaving a first refractive index and an electroactive material, disposedwithin the cavity and having a variable refractive index. Each beamsteering device further includes a first overlay, coupled to thesubstrate, to receive an incident light beam orthogonal to a first planeof the first overlay and to couple the incident light beam into theelectroactive material. Each beam steering device further includes asecond overlay coupled to the substrate and defining a second planetilted with respect to the first plane to define a tilt angle betweenthe first plane and the second plane, to receive the incident light beamfrom the electroactive material and to output, after refraction, theincident light beam as an output light beam. A first beam steeringdevice receives the incident light beam and outputs the output lightbeam as a first output light beam. Each subsequent beam steering devicereceives the output light beam of a previous beam steering device as itsinput light beam. Each beam steering device outputs is output light beamas refracted along a different axis than each other beam steering deviceof the set of beam steering devices.

All combinations of the foregoing concepts and additional conceptsdiscussed in greater detail below (provided such concepts are notmutually inconsistent) are part of the inventive subject matterdisclosed herein. In particular, all combinations of claimed subjectmatter appearing at the end of this disclosure are part of the inventivesubject matter disclosed herein. The terminology used herein that alsomay appear in any disclosure incorporated by reference should beaccorded a meaning most consistent with the particular conceptsdisclosed herein.

BRIEF DESCRIPTIONS OF THE DRAWINGS

The skilled artisan will understand that the drawings primarily are forillustrative purposes and are not intended to limit the scope of theinventive subject matter described herein. The drawings are notnecessarily to scale; in some instances, various aspects of theinventive subject matter disclosed herein may be shown exaggerated orenlarged in the drawings to facilitate an understanding of differentfeatures. In the drawings, like reference characters generally refer tolike features (e.g., functionally similar and/or structurally similarelements).

FIG. 1 illustrates light refraction according to Snell's Law.

FIG. 2A illustrates a beam steering device having a liquid crystalmaterial with its molecules aligned perpendicular to the device'soptical axis in the absence of an electric field.

FIG. 2B illustrates the beam steering device of FIG. 2A upon applicationof an electric field along the device's optical axis, with the moleculesof the liquid crystal material rotated with respect to the device'soptical axis.

FIG. 2C illustrates the beam steering device of FIG. 2A upon applicationof an electric field along the device's optical axis with a highervoltage than in FIG. 2B, with the molecules of the liquid crystalmaterial rotated more with respect to the device's optical axis.

FIG. 3A shows an inventive beam steering device with an electroactivematerial whose molecules are aligned with the device's optical axis inthe absence of an electric field.

FIG. 3B illustrates the beam steering device of FIG. 3A upon applicationof an electric field, with the molecules of the liquid crystal materialin a second alignment.

FIG. 3C illustrates the beam steering device of FIG. 3A upon applicationof an electric field with a higher voltage than in FIG. 3B, with themolecules of the liquid crystal material in a third alignment.

FIG. 4A illustrates the beam steering device of FIG. 3A in use, with anoutput beam refracted by a first degree.

FIG. 4B illustrates the beam steering device of FIG. 3A in use, with anoutput beam refracted by a second degree which is greater than the firstdegree of FIG. 4A.

FIG. 4C illustrates the beam steering device of FIG. 3A in use, with anoutput beam refracted by a third degree which is greater than the seconddegree of FIG. 4A.

FIG. 5A is a perspective view of the beam steering device of FIG. 4Awith front and back covers removed.

FIG. 5B is a perspective view of the beam steering device of FIG. 4Awith front and back covers in place.

FIG. 6A illustrates a smart contact lens with a beam steering devicelike the one shown in FIGS. 3A-3C.

FIG. 6B is a magnified view of the portion of the smart contact lens ofFIG. 6A showing the beam steering device.

DETAILED DESCRIPTION

Light beams can be redirected, or steered, by utilizing materials wherethe effective birefringence may be changed, resulting in a change in theindex of refraction. When light travels through one material andencounters another material of a different index of refraction, itsspeed changes as it propagates into the other material. If the lightexits one material and enters the next material at an angleperpendicular to the overlay between the materials, the light willchange speed but not propagation direction. However, if the light entersthe second material at an angle with respect the overlay between thematerials, the propagation direction of the light will change too. Thisphenomenon is called refraction and is described by Snell's Law

FIG. 1 illustrates refraction of light at the interface/boundary betweentwo media of different refractive indices n₂ and n₁, with n₂>n₁. Sincethe velocity in the second medium (v₂) is lower than in the first medium(v₁), i.e., v₂<v₁, the angle of refraction θ₂ is less than the angle ofincidence θ₁. Said another way, the light ray/beam in the higher-indexmedium is closer to the surface normal. Snell's law (also known asSnell-Descartes law and the law of refraction) is a formula used todescribe the relationship between the angles of incidence and refractiveindexes, when referring to light or other waves passing through aboundary between two different isotropic media, such as water, glass, orair. In optics, Snell's law is used in ray tracing to compute the anglesof incidence or refraction, and in experimental optics to find therefractive index of a material.

Snell's law states that the ratio of the sines of the angles ofincidence and refraction is equivalent to the ratio of phase velocitiesin the two media, or equivalent to the reciprocal of the ratio of theindices of refraction:

$\frac{\sin \mspace{14mu} \theta_{1}}{\sin \mspace{14mu} \theta_{2}} = {\frac{v_{1}}{v_{2}} = \frac{n_{2}}{n_{1}}}$

with each θ as the angle measured from the normal of the boundary, v asthe velocity of light in the respective medium (SI units are meters persecond, or m/s), λ as the wavelength of light in the respective mediumand n as the refractive index (which is unitless) of the respectivemedium.

In an example inventive beam steering device, two different materialsare abutted to one another at an interface/boundary. A light beam, orother electromagnetic beam, encounters this interface at an angle. Atleast one of the materials is an electroactive material that can changeits index of refraction. At one value of the index of refraction of theelectroactive material at this interface the beam changes its angle ofdirection by one amount, while at a second value of an index ofrefraction the light beam changes its angle of direction by a secondamount. If the index of refraction can be changed in discrete steps,then the light beam can be redirected in discrete angles. If the indexof refraction can be changed in an analog or continuous manner, then thelight beam's angle can also be changed in an analog/continuous manner.

Electroactive materials, for example, liquid crystals (LC), possess theability to change their index of refraction when the molecules areoriented in certain directions, i.e., they have a variable refractiveindex. If, for example, a nematic liquid crystal with elongatedmolecules that are oriented such that the long axis of the molecules isperpendicular to the direction of the light traveling through them, theindex of refraction may be 1.7 if the polarization of light is parallelto the long axis of the molecules. If the molecules are then reorientedsuch that the long axis is parallel to the direction of the lighttraveling through them, the index of refraction may change to 1.5.

FIGS. 2A-2C illustrate an example beam steering device 200 havingsubstrates 205 placed parallel to each other with a small gap betweenthem that can be less than about 1 jam, from about 1 jam to about 10jam, greater than 10 jam, including all values and sub-ranges inbetween. An electrically conductive but optically transmitting material,for example, Indium Tin Oxide (ITO), is coated on the surfaces of thesubstrates that are facing each other. These electrically conductivelayers are sometimes referred to as electrodes or electrode layers 210.Over the top of these electrodes is a layer of material that causesliquid crystal molecules to align parallel to the surface, or possiblyvertically if using a negative dielectric liquid crystal. Negativedielectric liquid crystals are available from Merck in Darmstadt,Germany. Such an alignment surface may be polyimide that has parallelmicro-grooves rubbed into its surface or other materials and processesto achieve the same effect, for example, UV-cured alignment materialsproduced by Rolic of Basel Switzerland, a BASF Company, or polyimidesproduced by Nissan Chemical of Japan. These surfaces are sometimesreferred to as alignment layers 215. The combination of anelectrode/electrode layer and its alignment layer can sometimes bereferred to as an overlay.

FIG. 2A illustrates how, when no electric field is applied by a circuit225 across the electrodes 210, the anchoring force of the alignmentlayer 15 causes the LC molecules 220 to align their long axes parallelto the substrates 205 and perpendicular to the optical axis 230 of thebeam steering device 200. In this condition, the index of refraction ofthe LC material 220 is a first value, for example, n=1.7.

In FIG. 2B, a small electric field is applied by the circuit 225 acrossthe electrodes 210, causing the long axis of the LC molecules 220 topartially rotate away from the alignment layers 15 and towards thedirection of the electric field, which is perpendicular to thesubstrates 205 and parallel to the optical axis 230 of the beam steeringdevice 200. When the electric field is of a relatively low value, forexample, 0.5 volts, the change-of-rotation force of the alignment layers215 upon the LC molecules 220 is greater than the force of the electricfield, so the LC molecules 220 rotate by a relatively small amount. Inthis state, the long axes of the LC molecules 220 are aligned moretowards the plane of the alignment layer 215 than in the direction ofthe electric field (i.e., perpendicular to rather than parallel to thesubstrates 205). In this situation, the index of refraction changes by asmall amount its total permissible range, for example, it may changefrom 1.7 to 1.62. generally, an example permissible range in refractiveindex for any of the beam steering devices disclosed herein can be lessthan 0.25, from about 0.25 to about 0.40, or greater than 0.40,including all values and sub-ranges in between.

In FIG. 2C, a higher voltage than that applied in FIG. 2B is applied bythe circuit 225, which creates a higher rotational force on the LCmolecules 220 than the force being applied by the alignment layers 215.As a result, the long axes of the LC molecules 220 align themselvesrelatively more with the direction of the electric field, and parallelto the optical axis 230, than with the plane(s) of the alignment layers215. In this situation, the index of refraction changes/reduces further,for example, it may change to 1.55. When the electric field is returnedto a lower voltage, or zero voltage, the anchoring force of thealignment layers 215 returns the LC molecules 220 to their initial stateof orientation shown in FIG. 2A.

The rate/speed of changing the orientation of the LC molecules from onewhere they are substantially parallel to the plane(s) of the alignmentlayers to substantially parallel to the direction of the electric fieldcan be influenced by the level of the voltage applied. If ahigher-than-required electric field is applied, i.e., higher thanrequired to rotate the LC molecules to a maximum permissible degree ofrotation, the rotation is faster than if the minimum-required voltage isapplied for attaining the maximum permissible degree of rotation.Generally, the minimum-required voltage can be a voltage required foraffecting rotation of the LC molecules, and can be from about 0.5 V toabout 3 V. In some cases, the minimum-required voltage can be lower than0.5 V, or can be higher than 3 V (e.g., 40 V or more), such as is thecase for some LC materials.

For example, if a beam steering device requires 5 V to fully rotate theLC Molecules to their maximum permissible orientation (e.g., 90 degrees)with the electric field, the time to rotate from the alignment layerorientation to the electric field orientation may be, for example, 300ms. However, if 10 V (i.e., greater than the minimum-required voltage of5 V) were applied, the time to rotate will be lower, for example, as lowas 100 ms. If 20 volts were applied, the time to rotate would be evenlower.

In another example, if the voltage required to rotate the LC materialfrom the alignment-layer orientation to midway between the two states(i.e., between alignment-layer orientation and electric-fieldorientation, as illustrated in FIG. 2B) is 2.3 V, and 2.3 V is applied,it may take, for example, 250 ms to complete this rotation. However, ifa higher voltage is applied, such as 5 V, it may traverse this rotationin 100 ms. To take advantage of this response without rotating the LCmolecules farther than desired, 5 V may be applied for 100 ms as the“speed” voltage, then switched to 2.3 V as the “holding voltage.” These“speed up” methods/approaches are sometimes known as overdriving the LCmaterial to attain a desired orientation. Despite overdriving, the speedat which the LC material returns towards its orientation with the planeof the alignment layer can be slow because the anchoring force of thealignment layer is weaker than the electric energy, and due to theelastic constants (e.g., the elastic modulus) of the LC material. Forexample, the molecules of a stiffer or more viscous material with ahigher elastic modulus will likely be slower in changing theirorientation to be with that of the alignment layer than one with a lowerelastic modulus. The result is that the speed of switching the lens fromthe OFF position (i.e., when the LC material is aligned with the planeof the alignment layer) to an ON position (i.e., when the LC material isat least partially aligned with the direction of the electric field) maybe increased by overdriving, but the speed of switching from ON to OFFcannot be increased in the beam steering device 200 by overdrivingbecause the only force that reorients the LC material is the relativelyweak force exerted by the alignment layer.

Beam Steering Devices

Disclosed herein are beam steering devices that can speed up the changein orientation of the liquid crystal molecules (and generally, anyelectroactive material that may be employed) when the orientation of theliquid crystal molecules is being adjusted in both directions. Toaccomplish this, two additional, similar substrates are attached to twosubstrates like those in FIGS. 2A-2C to form an LC cavity with atrapezoidal cross section, where the parallel sides are parallel to thedevice's optical axis. The alignment layer is optional for theseadditional substrates. One of the facets/substrates is not parallel toits opposite substrate and is instead at an angle or tilted with respectto it by, for example, less than about 1 degree, between about 1 degreeand about 60 degrees, greater than 60 degrees, including all values andsub-ranges in between. The substrates can be assembled such that theirrespective electrode layers are electrically insulated from each other.

FIGS. 3A-3C illustrate a beam steering device 300 that includes a firstoverlay 330, a second overlay 335, a third overlay 340, and a fourthoverlay 345 are shown. Each overlay may be coupled to a substrate, andmay include an electrode layer 360 (e.g., composed of an electricallyconductive and preferably optically transparent coating, such ITO,silver nanowires, PEDOT (poly(3,4-ethylenedioxythiophene), etc.) and anoptional alignment layer 355 (e.g., composed of rubbed polyimide, thoughany suitable material capable of affecting the alignment of theelectroactive material can be employed) as described for FIGS. 2A-2C. Analignment layer on one or more of the overlays 330, 335, 340 and 345aligns the liquid crystal material when the beam steering device 300 isin an unpowered state (i.e., when there is no electric field) andreduces discontinuities in the electroactive molecule/materialarrangement.

The substrate(s) that couple to the overlays 330, 334, 340, 345 can be asingular, continuous substrate or composed of multiple, discontinuoussubstrates; each of these possible substrate layouts is sometimescollectively referred to as a ‘substrate’ as well. Such a substrate canalso include any additional components (not shown), made of the same ordifferent material from the substrate, needed or desired to form asealed internal cavity 370 for holding an electroactive material. Forexample, the substrate can encompass or be coupled to the seals 350 thatmay be placed at each of the four corners of the device 300 toelectrically isolate the electrode layers of the overlays 330, 335, 340and 345 from each other, and to seal the cavity inside the device 300for the electroactive material 365, such as a liquid crystal material.Each substrate itself can have a characteristic, fixed refractive index(e.g., from about 1.3 to about 2.5, including all values and sub-rangesin between), and be composed of materials such as Glass, PMMA(polymethyl methacrylate), a polycarbonate, quartz, fused silica, andcombinations thereof. An example electroactive material within thecavity is a liquid crystal (e.g., Merck MLC-2140).

As shown in FIG. 3A, each overlay defines a plane, such that the firstoverlay 330 defines a plane P1, the second overlay 335 defines a planeP2, the third overlay 340 defines a plane P3, and the first overlay 345defines a plane P4. As illustrated, the plane P4 of the fourth overlay345 is not parallel to, and is tilted with respect to, the plane P3 ofits opposite overlay 340. On the other hand, the plane P1 of the firstoverlay 330 is substantially parallel to the plane P2 of its oppositeoverlay 335. As also illustrated in FIG. 3A, the device 300 can definean optical axis 375 with respect to which the orientation of theelectroactive material can be measured.

During example use of the beam steering device 300, an electric fieldmay be applied between any set of opposing overlays (e.g., the overlays330, 335) to induce liquid crystal rotation at a fast speed by utilizingthe overdriving method. Then that electric field may be removed andanother electric field may be applied to the other two opposing overlays(e.g., the overlays 340, 345), causing the liquid crystal to align alongthe axis of the new electric field. This can be accomplished, forexample, by using a single electric source, the output of which isswitched to affect generation of one electric field or the other. Insome cases, two sources can be used such that both electric fields aregenerated/present at the same time.

In the configuration of the device 300, overdriving can be applied intwo different directions (i.e., between both sets of overlays), allowingfaster rotation changes in both directions as compared to the device 200of FIGS. 2A-2C, where it is available in only one direction. The twoelectric fields can be present as one at any given time, in bothdirections simultaneously, or in a temporally overlapping manner. Thetwo electric fields can be generated using a single source, or with adifferent source for each electric field.

If both electric fields are substantially equal to each other inamplitude, the liquid crystal molecules can be held at an interimrotation within their total available/permissible rotation. If oneelectric field is greater than the other, the liquid crystal moleculeswill rotate and align to a greater degree in the direction of thestronger electric field. If one electric field is slightly greater thanthe other, the alignment direction will be slightly more along thedirection of the stronger electric field. As the stronger electric fieldis increased in strength relative to the weaker electric field, morerotation toward the stronger electric field occurs. By varying therelative strengths of the electric field in an analog fashion, rotationof the liquid crystal may be adjusted also in an analog fashion.Overdriving may also be used in the above described analog control,where a brief, larger-than-required voltage is applied.

If there is a homogenous alignment layer formed on overlays 330 and 335,the liquid crystal material 365 will align as shown in FIG. 3A, parallelto the planes P1, P2 of the overlays 330, 335, and along the opticalaxis 375. If an electric field is now applied between the overlays 340,345, then the liquid crystal molecules 365 will still align in the samedirection, but the electric field will be in addition to the alignmentforces provided by the alignment layer of overlays 330, 335. If thealignment layer is not present on overlays 330, 335, the electric fieldbetween the overlays 340, 345 would perform the alignment, however somediscontinuities may present themselves. In the orientation of thematerial 365 shown in FIG. 3A, the index of refraction of the material365 experienced by light traveling from left to right (i.e., from theoverlay 340 to the overlay 345) is at a minimum for the material 365 ifpolarized appropriately, and the index of refraction of the material 365to the same light traveling from top to bottom (i.e., between theoverlays 330, 335) is at its maximum.

FIG. 3B illustrates that the electric field between the overlays 340,345 is removed, while an electric field strong enough to cause fullrotation of the material 365 is applied across the overlays 330, 335,causing the molecules to align parallel to the plane P3 of the overlay340. The index of refraction of the liquid crystal to light travelingfrom left to right (i.e., from the overlay 340 to the overlay 345) isnow at its maximum if polarized appropriately, while the index ofrefraction to the same light traveling from top to bottom (i.e., betweenthe overlays 330, 335) in the figure would be at its minimum.

FIG. 3C illustrates that the electric field between the overlays 340,345 is removed, while an electric field strong enough to cause halfrotation of the material 365 is applied across the overlays 330, 335,causing the molecules of the material 365 to align halfway between beingvertically and horizontally aligned, i.e., tilted between the angles ofplanes P1, P3. FIG. 3C is, however, also illustrative of the state ofthe molecules of the material 365 when the field between the overlays340, 345 as well as the field between the overlays 330, 335 is present,and interact to align the molecules as illustrated. The index ofrefraction of the liquid crystal experienced by light traveling bothhorizontally (i.e., from the overlay 340 to the overlay 345) andvertically (i.e., between the overlays 330, 335) is approximately equal.As illustrated in FIG. 3B, a combination of a power source 380 and acontroller 385 can be used for generating and controlling application ofthe electric fields. The controller can be any suitable processingdevice configured to run and/or execute a set of instructions or codeassociated with operating the beam steering device 300. The controllercan be, for example, a general purpose processor, a Field ProgrammableGate Array (FPGA), an Application Specific Integrated Circuit (ASIC), aDigital Signal Processor (DSP), and/or the like.

FIGS. 4A-4C illustrate how variable beam steering can be accomplishedwith a beam steering device 400 that can be structurally and/orfunctionally similar to the device 300. In FIG. 4A, the electric fieldis in the same condition/state as described in FIG. 3A, applied betweenoverlays 440, 445. The index of refraction of the electroactive material(e.g., liquid crystal) inside of chamber/cavity 420 is equal to theindex of refraction at the overlay 440 (which is essentially the same asthe refractive index of the underlying substrate) for the incident lightbeam 480. The light beam 480 can be coupled into the overlay 440 in anysuitable manner, including free-space coupling and the use of couplingoptics such as optical fibers. Light beam 480 enters into, or isincident on, the overlay 440 perpendicular to its surface, so eventhough the index of refraction of the medium (typically air with anindex of 1) outside of overlay 440 is less than the index of refractionat the overlay 440, no refraction of light occurs because the angle ofincidence of the light onto the substrate is perpendicular. The lightbeam 480 can include one or more wavelengths, including visiblewavelengths (e.g., from about 400 nm to about 700 nm, including allvalues and sub-ranges in between), UV wavelengths (e.g., from 10 nm toabout 400 nm, including all values and sub-ranges in between), and IRwavelengths (e.g., from 800 nm to about 1 mm, including all values andsub-ranges in between).

The light beam 480 then travels through overlay 440 and enters theliquid crystal within cavity 420. Because the light beam 480 is stillperpendicular to the interface between the liquid crystal within thecavity 420 and the overlay 440, no refraction takes place, regardless ofthe index of refraction of the liquid crystal. Light beam 480 travelsthrough the liquid crystal within cavity 420 and enters the overlay 445.Although the overlay 445 is at a non-perpendicular angle of incidence tolight beam 480 (i.e., is tilted at a tilt angle ct with respect to theoverlay 440 as illustrated), no refraction occurs because the index ofrefraction of the liquid crystal and the overlay 445 are equal. Whenlight beam 80 exits the overlay 445, it encounters a different index ofrefraction (e.g., air again), so the angle between the exit surface ofthe overlay 445 and the light beam causes the light beam to be refractedat an angle 495. Input/incident light beam 480 is thus redirected intooutput light beam 490. Angle 495, sometimes referred to as the angle ofrefraction, is relatively small compared to those illustrated in FIGS.4B and 4C, described further below.

In FIG. 4B, the electric field is in the same condition/state asdescribed in FIG. 3B, applied between overlays 430, 435. The electricfield applied is not sufficient to fully align the liquid crystalmolecules to the electric field, and only partial rotation occurs. Theindex of refraction of the liquid crystal inside of chamber/cavity 320is now higher than the index of refraction at the overlay 440 for thelight beam 480. The light beam 480 enters into the overlay 440perpendicular to its surface, so even though the index of refraction ofthe medium outside of the overlay 440 is less than the index ofrefraction at the overlay 440, no refraction of light occurs because theangle of incidence of the light onto the overlay 440 is perpendicular.The incident/input light beam 480 then travels through the overlay 440and enters the liquid crystal within cavity 420. Because it is stillperpendicular to the overlay between the liquid crystal within thecavity 420 and the overlay 440, no refraction takes place, regardless ofthe index of refraction of the liquid crystal. Light beam 80 travelsthrough the liquid crystal within the cavity 420 and enters the overlay445. The overlay 445 is at a non-perpendicular angle to the direction oflight beam 480, and the index of refraction of the liquid crystal withincavity 420 is now higher than that of the overlay 445, resulting inrefraction of the light upward at the interface between the liquidcrystal and the overlay 445. When the light beam 480 exits the overlay445, it again encounters a different index of refraction of the newmedium it enters (e.g., air), so the angle between the exit surface ofthe overlay 445 and the light beam 480 causes the light beam to berefracted further by an angle 405. Light beam 480 is thus redirectedinto light beam 425. Angle 405 is larger than angle 495 in FIG. 4Abecause angle 405 is now the sum of the change in propagation fromrefraction of light that occurred at the liquid crystal-to-overlay 445boundary, plus the refraction of light that occurred at the overlay445-to-exit medium boundary, whereas the refraction of the light in FIG.4A occurred only at the overlay 445-to-exit medium boundary.

In FIG. 4C, the electric field is in the same condition/state asdescribed in FIG. 3C, applied to the overlays 430, 435. The electricfield applied between the overlays 430, 435 is now stronger than thesame field applied in FIG. 4B, and is sufficient in strength to fullyalign the liquid crystal molecules with that electric field. The indexof refraction of the liquid crystal inside of chamber/cavity 420 is noweven higher than the index of refraction in the condition described inFIG. 4B, and also higher than the overlay 430 for the incident/inputlight beam 480. Light beam 480 enters into overlay 440 perpendicular toits surface, so even though the index of refraction of the mediumoutside of overlay 440 is less than the index of refraction at theoverlay 440, no refraction of the light occurs because the angle ofincidence of the light onto the substrate is perpendicular. The lightbeam 480 then travels through overlay 440 and enters the liquid crystalwithin the cavity 420. Because the light beam 480 is still perpendicularto the boundary between the liquid crystal within the cavity 120 andoverlay 440, no refraction takes place, regardless of the index ofrefraction of the liquid crystal. The light beam 480 travels through theliquid crystal within the cavity 420 and enters the overlay 445. Thesubstrate 445 is at an angle to the direction of the light beam 480, andthe index of refraction of the liquid crystal within the cavity 420 isnow much higher than that of overlay 445, resulting in refraction of thelight at the boundary between the liquid crystal and the overlay 445.Due to the higher different in refractive index between the twomaterials, there is more refraction than that seen in FIG. 4B. When thelight beam 480 exits the overlay 445, it again encounters a differentindex of refraction of the new medium it enters, so the angle betweenthe exit surface of the overlay 445 and the light beam causes the lightbeam to deflect at an angle 415. The input light beam 480 is thusredirected/steered into output light beam 410. Angle 115 is larger thanangle 105 in FIG. 7B because angle 115 is now the sum of a greateramount of the refraction of light that occurred at the liquidcrystal-to-overlay, plus the refraction of light that occurred at thesubstrate-to-exit medium interface.

FIGS. 4A-4C illustrate three discrete settings that result in threedifferent values of refractive index for the liquid crystal material,resulting in three discrete angles of refraction of the output beam.However, the electric field applied to either set of overlays can bechanged in an analog and continuous manner, resulting in an analogchange in the amount of output beam steering that can be done. Forexample, one or both of the electric fields applied between the pairs ofoverlays can be swept such that the refractive index varies between aminimum or lower value to a maximum or higher value. The correspondingchange in refractive index can be linear or non-linear. Further, theoverdrive method described above can also be employed for any of theelectric fields described in FIGS. 4A-4C, resulting in much faster lightbeam angle changing/beam steering than could be accomplished withoutusing the overdrive method.

FIGS. 5A and 5B illustrate a 3D perspective view of a beam steeringdevice 500 (which can be structurally and/or functionally similar to thedevices 300, 400) formed as a 3D right trapezoid. The device 500includes overlays 530, 535 with planes that are parallel to each other,and an overlay 545 having a plane that is tilted with respect to that ofits opposing overlay 540. During use, the overlay 545 received anincident light beam, while the overlay 545 outputs an output light beamas explained with respect to FIGS. 3A-3C, 4A-4C. The interior of thedevice 500 defines a cavity 570 for holding the electroactive material.As illustrated in FIG. 5B, covers 580 may be placed at either end of thedevice 500 to seal the cavity 570, and at least one of the covers 580may be removable. The distance between the overlays 530, 535, thedistance between the overlays 540, 545, and/or the distance between thecovers 580, can independently be from about 1 m to about 15 m, includingall values and sub-ranges in between. The switching speed for changingthe degree of refraction for any of the beam steering devices 300, 400,500 can be from about 1 s to about 5 ms, including all values andsub-ranges in between.

As an example of comparative switching speeds, the beam steering device200 in FIGS. 2A-2C may be able to change the orientation of the LCmolecules 220 from alignment layer-orientation (FIG. 2A) to electricfield-orientation (FIG. 2C) in 10 ms in overdrive. However, it takes 50ms, upon removal of the electric field, for the LC molecules 220 tochange their orientation from electric field-orientation (FIG. 2C) backto alignment layer-orientation (FIG. 2A). In contrast, the beam steeringdevice 300 in FIGS. 3A-3C may be able to change the orientation of theLC molecules 365 from alignment layer-orientation (FIG. 3A) to electricfield-orientation (FIG. 3C) in 10 ms in overdrive, similar to the device200. However, upon removal of one electric field and application of theother (i.e., between the other pair of interfaces), the LC molecules 365now change their orientation from electric field-orientation (FIG. 3C)back to alignment layer-orientation (FIG. 3A) more quickly, and at asimilar rate due to the application of another field. So this change oforientation back to the alignment layer-orientation can also occur inabout 10 ms in overdrive mode for the device 300.

Applications

An example application of such beam steering devices is for multi-axisscanning (e.g., 2D/XY, or 3D, or generally nD scanning), which can finduse in various applications that would benefit from the improved beamsteering speeds achieved with these devices. In such applications, twoor more of these beam steering devices can be used in series/in acascade, with a first beam steering device receiving the initial inputlight beam and outputting an output light beam for consumption by thenext beam steering device, and so on. Each beam steering device canrefract its input light beam along a different axis that each other beamsteering device. For example, a first beam steering device in thecascade can receive the input light beam and output light beam asrefracted along (say) an X-axis. A second beam steering device ispositioned to receive this output light beam as orthogonal to itssurface and refract it along (say) a Y-axis. A third beam steeringdevice is positioned to receive this output light beam from the secondbeam steering device as orthogonal to its surface and refract it along(say) a Z-axis. The resulting output beam then can have specific XYZaddressability that is independently controllable for each axis.

Another example application of such beam steering devices is formulti-stage beam steering, such as for, for example, in an opticaldemultiplexing approach. A first stage can include a first beam steeringdevice that can be operated to receive an incident light beam and outputit as an output light beam (i.e., by selectively changing the refractiveindex of the electroactive material of the first beam steering device)that is refracted by discrete, predetermined amounts. For each degree ofrefraction that the output light beam can attain, the output light beamis coupled into a different beam steering device of a second stage,which can in turn be operated in any suitable manner depending on theapplication (e.g., to discard the light beam, to couple it to additionaldownstream optical components, etc.).

Yet another example application or use of such a beam steering devicecan be as a component in eyewear for generated virtual images. Forexample, such beam steering devices may be useful in smart contact lens,spectacle glasses, or head-mounted displays, to project a scanned imageinto the eye, such as in mixed or augmented reality (AR). AR devicescreate a virtual image that a user sees in addition to what is seen inthe real world. Conventional AR devices typically include a smalldisplay screen in conjunction with reflectors or mirrors to relay theimage to the eye. Adding such display screens to spectacle frames addsbulk and weight to the frames, while adding such display screens tocontact lenses is impossible. The present device replaces the displayscreen and overcome these limitations.

In the case of using the present technology in a smart contact lens, thebeam steering device can be fabricated such that the overall thickness(e.g., the distance between the overlays 540, 545 in FIGS. 5A-5B) can beless than the thickness of the contact lens, which is typically about0.1 mm thick. This device could include the light source, beam steeringdevice, and any collimating optics either as a single stack in line withthe optical axis of the eye, or with the use of mirrors if it is desiredthat some components be thicker and would cause the overall device to bethicker than required. For example, the light source could project thelight “sideways” or perpendicular to the eye's optical axis on theuser's retina, then be redirected along the eye's optical axis and intothe beam steering device. Any or all the components could be arrangedperpendicular to the eye's optical axis, then redirected to the eye'soptical axis with a mirror or reflecting component.

FIGS. 6A-6B illustrate example use of such a beam steering device withina smart contact lens 600, though it is readily applicable to anysuitable eyewear, such as any kind of lens (e.g., an intra-ocular lens),spectacles, and head-mounted displays to either project the beamdirectly into the eye, or project the beam onto a surface outside of theeye to paint/display the image. Here, the lens 655, in which a lightsource 670 and beam steering device 665 (which can be structurallyand/or functionally similar to the devices 300, 400, 500) are embedded,coupled to, and/or formed as a stack 665 embedded at location 650. Thelight source 670 can be configured, with or without coupling optics, togenerate a light signal as a spot (e.g., of image or video data) forprojection on the retina 660 of the user. The light signal can begenerated, for example, based on data received from a remote source,such as via an antenna coil or other network interfaces that is embeddedor coupled to the lens 655. A combination of a power source and acontroller, either of which may be embedded in or coupled to the lens655, can be used for controlling operation of the source 670 and thebeam steering device 665, and particularly for controlling generation ofthe light signal based on the received data. In addition to the beamsteering device being controlled by the controller to steer the beam,the controller could also switch the light source on and off so as tocreate individual points of light rather than continuous lines beingpainted. For clarity, one beam steering device is illustrated, but twoor more can be stacked in sequence as described above.

Then the beam steering device 665 can receive the light signal from thesource 670 directly or via coupling optics and steer/scan the spotaround to paint an image, or to render a video, on the retina 660, asdescribed for FIGS. 3A-3C, 4A-4C, and similar to how CRT televisiontubes painted an image onto a phosphorous screen. As described above,more than one beam steering device 665 can be employed to accomplish 2Dscanning of the image/video onto the retina 660. The orientation of thetilted surfaces can be positioned such that one device would steer thebeam in one direction while the other device steers the beam in theother direction, and can be generally orthogonal to each other. Thepower source and the controller can control generation of the electricfields of the beam steering device 665 for manipulating the refractiveindex of the electroactive material within the beam steering device 665.

CONCLUSION

While various inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariety of other means and/or structures for performing the functionand/or obtaining the results and/or one or more of the advantagesdescribed herein, and each of such variations and/or modifications isdeemed to be within the scope of the inventive embodiments describedherein. More generally, those skilled in the art will readily appreciatethat all parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the inventive teachingsis/are used. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific inventive embodiments described herein. It is,therefore, to be understood that the foregoing embodiments are presentedby way of example only and that, within the scope of the appended claimsand equivalents thereto, inventive embodiments may be practicedotherwise than as specifically described and claimed. Inventiveembodiments of the present disclosure are directed to each individualfeature, system, article, material, kit, and/or method described herein.In addition, any combination of two or more such features, systems,articles, materials, kits, and/or methods, if such features, systems,articles, materials, kits, and/or methods are not mutually inconsistent,is included within the inventive scope of the present disclosure.

Also, various inventive concepts may be embodied as one or more methods,of which an example has been provided. The acts performed as part of themethod may be ordered in any suitable way. Accordingly, embodiments maybe constructed in which acts are performed in an order different thanillustrated, which may include performing some acts simultaneously, eventhough shown as sequential acts in illustrative embodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

1. A method for projecting a light beam on a retina of a user viaeyewear worn by the user, comprising: receiving, via a network overlayof the eyewear, image data and/or video data from a remote device;converting, via a source of the eyewear, the image data and/or videodata into a light beam; coupling, into a beam steering device of theeyewear, the light beam as an incident light beam orthogonal to a firstplane of a first overlay of the beam steering device, the first overlaycoupled to a substrate of the beam steering device, the substrate havinga first refractive index, the substrate defining a cavity having anelectroactive material disposed therein, the electroactive materialexhibiting a variable refractive index; receiving, at a second overlayof the beam steering device, the incident light beam from theelectroactive material, the second overlay defining a second planetitled with respect to the first plane to define a tilt angle; applyinga first electric field to the electroactive material between the firstoverlay and the second overlay, and a second electric field to theelectroactive material between a third overlay and a fourth overlay ofthe beam steering device, the third overlay and the fourth overlay eachdefining a plane orthogonal with respect to the first plane, such thatthe electroactive material attains a second refractive index based on astrength of the first electric field and the second electric field; andoutputting, after refraction by the second overlay, the incident lightbeam as an output light beam onto the retina of the user.
 2. The methodof claim 1, wherein the applying the first electric field and the secondelectric field further comprises overdriving the electroactive materialinto attaining the second refractive index.
 3. The method of claim 1,wherein the applying the first electric field and the second electricfield further comprises sweeping the second refractive index between afirst value and a second value.
 4. The method of claim 3, wherein thesweeping includes continuously sweeping between the first value and thesecond value.
 5. The method of claim 3, further comprising, responsiveto the sweeping, steering the output light beam across the retina of theuser along a first axis.
 6. The method of claim 5, wherein the beamsteering device is a first beam steering device and the output lightbeam is a first output light beam, and wherein the outputting includescoupling the incident beam as the first output light beam into a secondbeam steering device of the eyewear, the method further comprisingsteering, by the second beam steering device, the first output lightbeam as a second output light beam across the retina of the user along asecond axis.
 7. The method of claim 1, wherein the applying the firstelectric field includes applying a first electrical signal to anelectrode layer of the first overlay and to an electrode layer of thesecond overlay, and wherein the applying the second electric fieldincludes applying a second electrical signal to an electrode layer ofthe third overlay and to an electrode layer of the fourth overlay. 8.The method of claim 1, wherein the eyewear includes an augmented realitydevice.
 9. The method of claim 1, wherein the eyewear includes a contactlens.
 10. The method of claim 1, wherein the eyewear includes spectacleglasses.
 11. The method of claim 1, wherein the eyewear includes anaugmented reality device, and wherein the augmented reality device doesnot include a display.
 12. The method of claim 1, wherein the outputtingincludes outputting the output light beam in a direction different froman optical axis of the eye of the user, and the method furthercomprising steering, via a reflecting component of the eyewear, theoutput light beam along the optical axis of the eye and onto the retinaof the user.
 13. The method of claim 1, wherein the outputting includesoutputting the output beam along an optical axis of the eye of the user.